Sen. Jeff Merkley of Oregon was the first Democratic senator to endorse Bernie Sanders in 2016, but he’s holding back ahead of the 2020 primary, saying Sunday there are plenty of bold Democrats in the field.

Mr. Merkley, a Democrat and staunch progressive, used a New York Times op-ed to throw his lot behind Mr. Sanders, the revolutionary from Vermont, during the last campaign.

Speaking to NBC on Sunday, he said there are “a lot of capable individuals” in the new race who understand “kitchen table” issues and can take on President Trump.

“This is no longer a Hillary Clinton and Bernie Sanders [race]. Hillary Clinton is not a candidate,” he told Meet the Press. “So we have a different set of cards this time, and I’m looking forward to hearing from all of them.”

Mr. Sanders is toward the head of the pack in the crowded Democratic field of over 20 declared candidates, though he tends to trail former Vice President Joseph R. Biden in polls.

The Vermont independent, who caucuses with Senate Democrats, charmed a progressive left disenchanted by the establishment and Mrs. Clinton in 2016. Yet this time, several of his primary rivals have espoused bold liberal ideas like single-payer health care or free college.

Mr. Merkley said that’s a good thing, and he’s looking for a robust debate before he endorses.

“I’m really looking forward to them laying out that vision, getting America excited about returning to the fundamentals of taking on health care, and housing, and education, infrastructure, living-wage jobs, the things that have been incredibly neglected and set aside by this administration,” he said. “I feel that there are many capable individuals who are making this case.”